1. Field of the Invention
The present invention relates to a liquid crystal display apparatus for use as a monitor display in a computer and for displaying a video image or the like, and more particularly to a liquid crystal display apparatus which is excellent in display quality and visual angle characteristics.
2. Description of the Related Art
White/black display brightness contrast (hereafter simply referred to as xe2x80x9ccontrastxe2x80x9d) is relevant to the display quality of a liquid crystal display apparatus. Causes of degrading the contrast include a phenomenon in which light leaks through spherical spacers or through the vicinity thereof when a black color is displayed. As techniques to eliminate degradation of contrast due to such a light-leakage phenomenon, for example, a liquid crystal display apparatus disclosed in Japanese Unexamined Patent Publication JP-A 2-15241 (1990), a method for manufacturing a liquid crystal display panel disclosed in Japanese Unexamined Patent Publication JP-A 4-204417 (1992), and others are known.
The liquid crystal display apparatus disclosed in JP-A 2-15241 comprises a thin-film transistor substrate including a substrate and thin-film transistor arrays arranged in a matrix form thereon, and a counter electrode substrate including a transparent substrate, and a transparent counter electrode and a transparent insulating film formed on a transparent substrate. In this construction, a gap between the thin-film transistor substrate and the counter electrode substrate is defined with conductive columns formed on source electrode lines of the transistors by vapor-deposition, sputtering or the like. On the other hand, in the method for manufacturing a liquid crystal display panel disclosed in JP-A 4-204417, spacer particles are positively or negatively charged, the transparent electrode formed on a glass substrate is given the same pole as that of the spacer particle, and the spacer particles are dispersed. In this way, by forming and dispersing spacers on the underside of a light-shielding material, such as a metal wire, an active element, or a black mask, or on a pattern gap, i.e., a region other than the display electrode region, it is possible to prevent occurrence of light leakage due to a spacer.
However, the liquid crystal display apparatus disclosed in JP-A 2-15241 and the method for manufacturing a liquid crystal display panel disclosed in JP-A 4-204417 have the following disadvantages. The former requires a column forming process, and, in this regard, unevenness in the heights of columns inconveniently causes a gap between the substrates to become uneven. This makes it difficult to realize a liquid crystal display apparatus in which the substrates are equally spaced with high accuracy. The latter requires a light-shielding portion to have an area large enough to disperse spherical spacers. This accordingly imposes a restriction on the size of the opening portion excluding the light-shielding portion. Consequently, it is difficult to increase the transmittance of the liquid crystal display apparatus.
Moreover, there arises another problem. Due to the wavelength-dependent property existing in the spectral characteristics of a polarizing plate, liquid crystal, a phase difference plate, and other materials, the black display of a liquid crystal display apparatus is tinged with blue. Since the bluish tint occurs only in black display, there is a problem that if color adjustment is performed to solve this bluish tint problem, the color of white display also varies.
Furthermore, in a liquid crystal display apparatus with a wide viewing angle comprising: a liquid crystal layer having a display picture element region including a first and a second region having mutually different liquid crystal molecule orientations; and a phase difference compensating element for compensating for, in a state where no voltage is applied, the refractive index anisotropy of the liquid crystal molecules aligned substantially parallel to the substrate surface, light leakage due to a spherical spacer is more notable and the bluish tint of black display is deeper than in a common twisted nematic mode construction.
An object of the invention is to provide a liquid crystal display apparatus offering high contrast and excellent display quality, with its substrates equally spaced with high accuracy.
The invention provides a liquid crystal display apparatus comprising:
a first and a second substrate, of which at least one is transparent;
color filters of a plurality of colors formed on at least one of the substrates;
a spacer for defining a gap between the first and second substrates,
wherein a density of spacers existing in a color filter region of any one of the colors is lower than a density of spacers existing in a color filter region of at least one of remaining, colors.
According to the invention, the density of the spacers existing in the color filter region of any one of the colors is lower than that of the spacers existing in the color filter region of the at least one of remaining colors. This arrangement helps prevent occurrence of light leakage due to the spacer and thus makes it possible to keep the brightness of black display low and to improve the contrast.
As described heretofore, according to the invention, light leakage due to a spacer can be successfully prevented. This makes it possible to keep the brightness of black display low, to allow substrates to be equally spaced with high accuracy, to obtain higher transmittance, and to improve the contrast.
The invention further provides a liquid crystal display apparatus comprising:
a first and a second substrate, of which at least one is transparent;
a color filter of a plurality of colors formed on at least one of the substrates;
a liquid crystal layer contained between the first and second substrates; and
a spacer for defining a gap between the first and second substrates,
wherein, in the liquid crystal layer, display picture element regions have at least two regions which have mutually different liquid crystal molecule orientations,
and wherein a density of spacers existing in a color filter region of any one of the colors is lower than a density of spacers existing in a color filter region of at least one of remaining colors.
According to the invention, there is provided a liquid crystal layer in which display picture element regions have at least two regions having mutually different liquid crystal molecule orientations. Moreover, the density of spacers existing in the color filter region of any one of the colors is lower than the density of spacers existing in the color filter region of at least one of remaining colors. This arrangement makes it possible to attain wide-angle-view characteristics and to prevent occurrence of light leakage due to a spacer. Consequently, the brightness of black display is kept low and the contrast is improved.
Further, according to the invention, wide-angle-view characteristics are attained and occurrence of light leakage due to a spacer can be prevented. This makes it possible to keep the brightness of black display low, to allow substrates to be equally spaced with high accuracy, to obtain higher transmittance, and to improve the contrast.
Further, in the invention, it is preferable that a density of spacers existing in a color filter region of a color having higher visibility for human eyes is lower than a density of spacers existing in a color filter region of a color having lower visibility for human eyes.
According to the invention, the density of spacers existing in the color filter region of a color having higher visibility for human eyes is lower than the density of spacers existing in the region corresponding to a color having lower visibility for human eyes. This helps prevent light leakage due to a spacer from occurring in light of a color having higher visibility for human eyes, and thereby keep the brightness of black display low and improve the contrast.
In the invention, it is preferable that the color filters are of three colors: red, green, and blue, and that a density of spacers existing in a color filter region of green-color is lower than a density of spacers existing in a color filter region of red- or blue-color.
According to the invention, the density of spacers existing in the color filter region of green-color is lower than the density of spacers existing in the color filter region of red- or blue-color. This helps prevent light leakage due to a spacer from occurring in green light having higher visibility for human eyes, and thus keep the brightness of black display low and improve the contrast.
Further, according to the invention, light leakage due to a spacer is prevented from occurring in green light having higher visibility for human eyes. This makes it possible to keep the brightness of black display low and to improve the contrast.
In the invention, it is preferable that the color filters are of three colors: red, green, and blue, and that a density of spacers existing in a color filter region of green- or blue-color is lower than a density of spacers existing in a color filter region of red-color.
According to the invention, the density of spacers existing in the color filter region of green- or blue-color is lower than the density of spacers existing in the color filter region of red-color. This helps prevent light leakage due to a spacer from occurring in green light having higher visibility for human eyes under photopic conditions of vision and in blue light having higher visibility for human eyes under scotopic conditions of vision. Consequently, the brightness of black display is kept low, the contrast is improved, and a bluish tint is suppressed.
Moreover, according to the invention, it is possible to prevent light leakage due to a spacer from occurring in green light having higher visibility for human eyes under photopic conditions of vision and in blue light having higher visibility for human eyes under scotopic conditions of vision. Consequently, the brightness of black display is kept low, the contrast is improved, and a bluish tint is suppressed